This invention relates generally to pipettes and more particularly to pipettes of the repetitive liquid dispensing type.
Hand-held liquid dispensing pipettes have become very popular in recent years for use in laboratories in conducting chemical tests. A principal use of such devices is in medical and clinical laboratories wherein precise volumes of liquid and a specimen under test need to be mixed together. Such a pipette includes a piston cylinder and a piston sealed thereto. An end of the pipette that is in fluid communication with the piston cylinder is submersed in the liquid to be transferred, a precise volume drawn up, usually in a detachable tip, this liquid being discharged by the pipette into another container. Such liquid transfer pipettes are illustrated in U.S. Pat. Nos. RE 27,637; 3,855,867; 3,918,308 and 3,882,729.
Another type of pipette in use in chemical and medical laboratories is one wherein a volume of liquid is drawn into the pipette and thence a known portion of that volume is dispensed each time the pipettor knob is depressed. Such a repetitive dispenser type of pipette is described in U.S. Pat. No. 3,161,323, a device substantially as shown in that patent having been sold by the assignee thereof for many years. A similar device is being manufactured and sold by Unimetrics Universal Corporation of Anaheim, California.
It is a principal object of the present invention to provide an improved pipette of the liquid dispensing type capable of accurate liquid volume dispensing and which is convenient to use.